1. Field of the Invention
The present invention relates to interactive computer systems, and in particular to method and apparatus for facilitating wireless, full-body interaction between a human participant and a computer-generated graphical environment.
2. Description of the Related Art
So-called "virtual reality" ("VR") systems enable users to experience computer-generated environments instead of merely interacting with them over a display screen. Such systems typically require the user to don goggles, through which s/he perceives the virtual environment, as well as sensors that encode the user's gestures as electrical signals. The user reacts naturally to the changing virtual environment, generating signals that the computer interprets to determine the state and progress of the presented environment.
In order to encode a sufficiently broad spectrum of gestures to facilitate natural interaction, VR systems ordinarily require the user to wear, in addition to the goggles, at least one "data glove" to detect hand and finger movements, and possibly a helmet to detect head movements. Full-body systems, which encode movements from numerous anatomical sites to develop a complete computational representation of the user's overall body action, require many more sensors; however, such systems, would be capable of projecting the user fully into the virtual environment, providing him or her with greater control and a heightened sense of participation ideally suited to interactive simulations.
Unfortunately, numerous practical difficulties limit the capacity of current VR systems to achieve this goal. The nature of the interaction currently offered, even with full-body sensor arrays, is usually rather limited. The computational demands placed on a system receiving signals from many sensors can easily overwhelm even large computers, resulting in erratic "jumps" in the visual presentation that reflect processing delays. Moreover, no matter how many sensors surround the user, they cannot "see" the user, and therefore cannot integrate the user's true visual image into the virtual environment.
Economic and convenience factors also limit sensor-type VR systems. As the capabilities of VR systems increase, so do the cost, awkwardness and inconvenience of the sensor array. The sensors add weight and heft, impeding the very motions they are intended to detect. They must also ordinarily be connected, by means of wires, directly to the computer, further limiting the user's movement and complicating equipment arrangements.
In order to overcome the limitations associated with sensor-based VR systems, researchers have devised techniques to introduce the user's recorded image into a virtual environment. The resulting composite image is projected in a manner visually accessible to the user, enabling the user to observe his or her appearance in and interaction with the virtual environment.
Two such approaches include the VideoPlace system (see, e.g., M. Krueger, Artificial Reality II (1991) and U.S. Pat. No. 4,843,568) and the Mandala system (see, e.g., Mandala VR News, Fall/Winter 1993; Vincent, "Mandala: Virtual Village" and Stanfel, "Mandala: Virtual Cities," Proceedings of ACM SIGGRAPH 1993 at 207-208 (1993)). Unfortunately, these systems exhibit various limitations. For example, Krueger's VideoPlace requires a special background and ultraviolet lamps, and extracts and represents only the user's silhouette. The Mandala system can integrate the user's full image within the virtual environment it creates, but requires a a chroma-key blue background. Both systems are limited to two-dimensional VR representations (i.e., the user can only navigate up-down and left-right in the virtual world, and represented objects cannot be located in front of or behind the user). Both the VideoPlace and Mandala systems can process only a limited range of gestural information.